Section: POSIX Programmer's Manual (3P)
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
--- decompose a floating-point number
double modf(double x, double *iptr);
float modff(float value, float *iptr);
long double modfl(long double value, long double *iptr);
The functionality described on this reference page is aligned with the
ISO C standard. Any conflict between the requirements described here and the
ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C standard.
These functions shall break the argument
into integral and fractional parts, each of which has the same sign as
the argument. It stores the integral part as a
function), or a
function), in the object pointed to by
Upon successful completion, these functions shall return the signed
fractional part of
is NaN, a NaN shall be returned, and *iptr shall be set to a
is ±Inf, ±0 shall be returned, and *iptr shall be set to
No errors are defined.
The following sections are informative.
function computes the function result and *iptr
a = modf(x, iptr) ;
x == a+*iptr ;
allowing for the usual floating-point inaccuracies.
The Base Definitions volume of POSIX.1-2008,
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
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